As president, Ronald Reagan spoke movingly of the shock and horror he felt as part of a military film crew documenting firsthand the atrocities of the Nazi death camps.

The story wasn’t true.

Years later, an adamant, finger-wagging Bill Clinton looked straight into a live TV camera and told the American people he never had sex with White House intern Monica Lewinsky.

He was lying.

Presidents of all stripes and both major political parties have bent, massaged or shaded the truth, elided uncomfortable facts or otherwise misled the public — unwittingly or, sometimes, very purposefully.

Trump and Congress may make it easier to get drugs approved — even if they don’t work »

“It’s not surprising,” said Charles Lewis, a journalism professor at American University who wrote a book chronicling presidential deceptions. “It’s as old as time itself.”

But White House scholars and other students of government agree there has never been a president like Donald Trump, whose volume of falsehoods, misstatements and serial exaggerations — on matters large and wincingly small — place him “in a class by himself,” as Texas A&M’s George Edwards put it.

“He is by far the most mendacious president in American history,” said Edwards, a political scientist who edits the scholarly journal Presidential Studies Quarterly. (His assessment takes in the whole of Trump’s hyperbolic history, as the former real estate developer and reality TV personality has only been in office since Jan. 20.)

Edwards then amended his assertion.

“I say ‘mendacious,’ which implies that he’s knowingly lying. That may be unfair,” Edwards said. “He tells more untruths than any president in American history.”

The caveat underscores the fraught use of the L-word, requiring, as it does, the certainty that someone is consciously presenting something as true that they know to be false. While there may be plenty of circumstantial evidence to suggest a person is lying, short of crawling inside their head it is difficult to say with absolutely certainty.

When Trump incessantly talks of rampant voter fraud, boasts about the size of his inaugural audience or claims to have seen thousands of people on rooftops in New Jersey celebrating the Sept. 11 attacks, all are demonstrably false. “But who can say if he actually believes it,” asked Lewis, “or whether he’s gotten the information from some less-than-reliable news site?”

Reagan, who is now among the most beloved of former presidents, was famous for embroidering the truth, especially in the homespun anecdotes he loved to share.

In the case of the Nazi death camps, there was some basis for his claim to be an eyewitness to history: Serving stateside in Culver City during World War II, Reagan was among those who processed raw footage from the camps. In the sympathetic telling, the barbarity struck so deeply that Reagan years later assumed he had been present for the liberation.

Even when he admitted wrongdoing in the Iran-Contra arms-for-hostages scandal, which cast a dark stain on his administration, Reagan did so in a way that suggested he never meant to deceive.

“A few months ago I told the American people I did not trade arms for hostages,” Reagan said in a prime-time address from the Oval Office. “My heart and my best intentions still tell me that’s true, but the facts and the evidence tell me it is not.”

Clinton, who famously parsed and tweezed the English language with surgical precision, offered a straight-up confession when admitting he lied about his extramarital affair with Lewinsky, which helped lead to his impeachment.

“I misled people, including even my wife,” Clinton said, a slight quaver in his voice as he delivered a nationwide address. “I deeply regret that.”

President Obama took his turn apologizing for promising “if you like your healthcare plan, you can keep it” under the Affordable Care Act; millions of Americans found that not to be true, and PolitiFact, the nonpartisan truth-squad organization, bestowed the dubious 2013 “Lie of the Year” honor for Obama’s repeated falsehood.

“We weren’t as clear as we needed to be in terms of the changes that were taking place,” Obama said in an NBC interview. “I am sorry that so many are finding themselves in this situation based on assurances they got from me.”

Speaking at CIA headquarters, President Trump falsely accused the media of creating a feud between himself and the intelligence community.

(Andrew Harnik / Associated Press)

Trump, by contrast, has steadfastly refused to back down, much less apologize, for his copious misstatements. Rather, he typically repeats his claims, often more strenuously, and lashes out at those who point out contrary evidence.

“There’s a degree of shamelessness I’ve never seen before,” said Lewis, the American University professor, echoing a consensus among other presidential scholars. “There’s not a whole lot of contrition there.”

Sean Spicer, the White House press secretary, has suggested Trump is unfairly being held to a more skeptical standard by a hostile press corps. “I’ve never seen it like this,” he said at one of his earliest briefings. “The default narrative is always negative, and it’s demoralizing.”

Gil Troy, a historian at Montreal’s McGill University, agreed the relationship between the president and those taking down his words has changed from the days when a new occupant of the White House enjoyed a more lenient standard — at least at the start of an administration — which allowed for the benefit of the doubt.

That, Troy said, is both Trump’s fault — “he brings a shamelessness and blatancy” to his prevarications that is without precedent — and the result of a press corps “that feels much more emboldened, much more bruised, much angrier” after the antagonism of his presidential campaign.

Since taking office, there has been no less hostility from on high; rather, echoing his pugnacious political strategist, Stephen K. Bannon, Trump has declared the media to be the “opposition party.”

“We’re watching the birth pangs of a new press corps and a new series of protocols for covering the president,” Troy said.

It is sure to be painful all around.

[email protected]

@markzbarabak

ALSO

White House whoppers: Six times a president misled the public

How the Senate’s once-revered traditions are falling victim to partisan divide

How a top conservative radio host took on Trump, lost his audience and faith, but gained a new perspective